[ad_1]
Selective breeding by humans has led to some incredibly weird and unhappy pets over the years, and Alfort’s Leaping Rabbit is among the strangest of the bunch.
This rare breed of rabbit does not jump or walk like any other rabbit or hare in existence. When the jumper is ready to go, he throws his hind legs in the air and bounces on his front legs, like a human acrobat stepping on their hands.
While this might sound like a fun trait, it unfortunately comes with other debilitating issues. Now, the one rabbit that can’t jump properly has helped us better understand the genetics of jumping in mammals.
Crossing a single male jumper with a single white New Zealand female, and then crossing the resulting offspring, the researchers bred 52 rabbits, 23% of which carried two copies of the mutant gene similar to the original sire. These figures correspond to the statistics expected when there is only one recessive gene involved in a mutation.
By pooling the DNA of the jumper and the young non-jumper, the researchers used whole genome sequencing to compare the two groups. In the end – as they expected – there was only one gene that stood out.
The cause of the defective jumper jump appears to lie in a mutation in a conserved evolutionary site of a gene known as RORB, which provides instructions to mammalian cells so that they can create certain proteins.
https://www.youtube.com/watch?v=gxUKMqNX2Uw
RORB proteins are typically found throughout the nervous system of the rabbit, where they help turn the genetic code into a model for building proteins. This particular mutation, however, causes a particularly sharp decrease in the number of neurons in the spinal cord that can actually produce this protein.
In fact, two copies of the RORB mutation did not result in any protein in the spinal cord, which was linked to an inability to jump. Other rabbits in the litter that were able to jump with their hind legs did not show such a loss of protein.
The RORB gene, the authors conclude, must be what allows rabbits to bind together. It could also be the key to jumping other mammals.
Over the years, there has been a great deal of scientific interest in the special physiology and biomechanics that allow mammals – like kangaroos, rabbits, hares, and some mice – to jump, but the underlying genetics of this exploit was rarely taken into account.
One of the few recent studies found that mice with the same RORB mutation as jumping rabbits also couldn’t jump as usual. Instead, these rodents waddle on their front legs like a duck, with their tails and hind legs in the air.
“I spent four years watching these mice making little palm rests, and now I see a rabbit doing the same pear tree,” neuroscientist Stephanie Koch of University College London told Science News. “It’s incredible.”
Koch’s study in rabbits is the first to describe a specific gene needed to jump or jump, and it aligns extremely well with what she has observed in mutant mice.
Similar to mutant rodents, jumping rabbits also exhibit other anatomical flaws beyond their odd walk. Many are born blind and develop cataracts in their first year of life. RORB knockout mice also exhibit retinal degeneration.
In mice, the RORB gene appears to play an essential role in the differentiation of cells in the cerebral cortex and the retina. It could also do something similar in the spinal cord, which is involved in the regulation of sensory information and locomotion in mammals.
As such, this lack of protein could be what causes the hind legs of rabbits and mice to lift up instead of jumping. In jumping rabbits, for example, the RORB mutation appears to cause defects in the differentiation of interneurons in the spinal cord, although this is not really the cause of the bizarre locomotion.
“Besides its expression in the spinal cord, MMR is also expressed in many regions of the brain such as the somatosensory, auditory, visual and primary motor cortex, in certain nuclei of the thalamus and hypothalamus, in the pituitary and in the superior colliculus. ”write the authors.
“Thus, we cannot exclude the possibility that an alteration of RORB function in the brain contributes to the locomotion phenotype characteristic of jumping rabbits.”
The effects of the RORB mutation will require more study, but it is evident that it is involved in one way or another. This was the only variant identified in the entire genomic sequence of rabbits that impacted the jump.
While there may be more genes involved in rabbit hopping, it looks like the poor jumping rabbits certainly pointed us in the direction of one.
The study was published in PLOS Genetics.
[ad_2]
Source link